SCJP : Inner Classes Mock Exam Practice Questions

Questions no -1 
What is the output for the below code ?

public class Outer {
	private int a = 7;
	   
	   class Inner {
	      public void displayValue() {
	         System.out.println("Value of a is " + a);
	      }
	   }
	}


public class Test {
	
	public static void main(String... args) throws Exception {
		Outer mo = new Outer();     
		  Outer.Inner inner = mo.new Inner();
		  inner.displayValue();

	}
	
}




options
A)Value of a is 7
B)Compile Error - not able to access private member.
C)Runtime Exception
D)Value of a is 8

Correct answer is : A

Explanations : An inner class instance can never stand alone without a direct relationship to an instance of the outer class.
you can access the inner class is through a live instance of the outer class.
Inner class can access private member of the outer class.

Questions no -2 
What is the output for the below code ?

public class Tech {
	 public void tech() {
	      System.out.println("Tech");
	   }

}


public class Atech {

	Tech a = new Tech() {	      
	      public void tech() {
	         System.out.println("anonymous tech");
	      }
	   };
	   
	   public void dothis() {
		      a.tech();     
		      
		   }

public static void main(String... args){
	Atech atech = new Atech();
	atech.dothis();
}




options
A)anonymous tech
B)Compile Error 
C)Tech
D)anonymous tech Tech

Correct answer is : A

Explanations : This is anonymous subclass of the specified class type.
Anonymous inner class ( anonymous subclass ) overriden the Tech super class of tech() method.
Therefore Subclass method will get called.

Questions no -3 
What is the output for the below code ?

public class Outer {
	 private String x = "Outer variable";
	   void doStuff() {
	     String z = "local variable";
	     class Inner {
	       public void seeOuter() {
	         System.out.println("Outer x is " + x);
	         System.out.println("Local variable z is " + z);  
	       } 
	     }   
	   }  
	   
	  
}




options
A)Outer x is Outer variable.
B)Compile Error 
C)Local variable z is local variable.
D)Outer x is Outer variable Local variable z is local variable

Correct answer is : B

Explanations : Cannot refer to a non-final variable z inside an inner class defined in a different method.